1. Field of the Invention
The present invention relates to an electromagnetic wave absorber used mostly to cover inner surfaces of an anechoic chamber and to an electromagnetic wave absorption structure.
2. Description of the Related Art
Inner surfaces of such the anechoic enclosure, namely ceiling, side walls and sometimes floor of the anechoic chamber utilized for measuring radio characteristics of an electronic equipment disposed therein will be covered by arrays of electromagnetic wave absorbers. These absorbers are in general made from solid ohmic loss material in the form of wedges or pyramids. Tapered shape (wedge or pyramid) of the absorbers is advantageous for attenuating reflections of waves because the input impedance of the absorbers against the incidence waves will gradually change.
However, the weight of the absorbers of such the solid type becomes very heavy because one meter or more height is required for obtaining sufficient energy absorption. The heavier of the absorbers, the more difficult of transportation and installation of the absorbers. Also, if the absorbers are very heavy, it may be fallen from the walls after installation and the transportation cost will greatly increase. Furthermore, the material cost of the solid type absorbers is extremely high.
In order to reduce the weight of the absorber, a monoblock absorber having hollow pyramid shape has been proposed (Japanese Patent Unexamined Publication No. 4(1992)-44300 and Japanese Utility Model Unexamined Publication No. 3(1991)39898). However, this absorber is not only very difficult for producing but also easily damaged during the transportation because of its poor strength. Furthermore, since each of the absorbers is of great bulk and cannot be disjointed during transportation and installation, the transportation cost is extremely high and the installation of the absorber to the wall is very difficult.